Do I need a TEFL?

I'm going to Japan in March with no degree and no TEFL (or any such qualification). I understand the easiest job to get is as an English teacher, but also that it's harder to get a job with neither a degree nor TEFL. I do actually have a little teaching experience, but not much.
I'm not wanting an especially good job, maybe just part-time, but something that'll bring in some money. I'd like to do just some quite casual conversational stuff, rather than particularly serious teaching (I think I'd be much better at it).
What sort of job can I reasonably expect to get, and what sort of wage will I be earning? (I'm thinking on a monthly basis really)

I will have a working holiday visa. Living in Tokyo.

Thanks very much for your help.

I really don't like your chances on getting even a poor English teaching job. You won't be able to get a working visa so the only people that would consider hiring you would be extremely shifty people who will probably take advantage of you because you will be in no situation to do anything about it. Your only hope would be to do private lessons, but finding students will be very difficult I would imagine.

@the man:

James will have a working holiday visa so can work legally as soon as he arrives.

@James, the market for English teaching has got very competitive in the last couple of years. It's very difficult to give you even a ballpark figure for part time work, since hours can vary so much.

You might get around 2,500 yen an hour for private lessons, but it will take you a while to build up a student base.

I know a teacher who's been in Japan for 20+ years and he's having a hard time finding part time work to cover his bills.

Even I struggle at times to break even. The only thing I can say is, it sounds easy until you actually try it. ("Teaching" English, if that is what we can call it). Takes a lot of time and energy.

Just send your resume to everyone and everywhere and hope one bites, that's the only thing you can do. Pay can range from 1500yen for gabagoons to 3000yen an hour depending on school/company. Hours vary as well but expect evenings when students are not working.